Shape of intrinsic alpha pulse height spectra in lanthanide halide scintillators

We found that α-γ mixed events have higher light yield than expected for alpha particles alone, which leads to overestimation of the α/β ratio when it is measured with internal 227Th and 223Ra isotopes. The time-amplitude analysis showed that the α peaks of 219Rn and 215Po in LaBr3(Ce) and LaBr3(Ce,Sr) are not symmetric. We compared the simulation results with the measured data and provided further evidence of the important role of mixed α-γ-electron events for understanding the shape of the internal α spectrum in scintillators.